Improve UrlMappings to allow specifying of HTTP method as a prefix to the mapping

Currently outside of the resource mappings you have to do:

```
 "/books"(controller:"book", method:"GET")
```

It is more readable of the HTTP method can be specified before. So we should allow:

```
get "/books"(controller:"book")
```

Note Groovy doesn't allow fully upper case method names like `GET` so lower case is used
